1. An extracellular, proteolytic enzyme has been observed in more than 30 strains of beta type, aerobic and facultative hemolytic streptococci.
2. The enzyme is readily demonstrable in sterile filtrates of cooked meat cultures.
3. No gas or foul odor is produced.
4. It is partially inactivated by exposure to about 60°C. for 45 minutes or longer.
5. The enzyme manifests itself in cooked meat cultures after about 48 hours incubation at 37°C. The sterile filtrate from a 10 day old culture acts within 18 hours.
6. From 50 to 75 per cent of the meat in a tube of cooked meat medium may be digested in about 3 weeks at room temperature after 5 days initial growth at 37°C.
7. No correlation is found, in the cases studied, between hemolysis and proteolysis.
8. Streptococci not digesting beef tissue will not digest human tissue, and those which do digest beef tissue also digest human tissue. This conclusion applies only to the nine strains studied.
9. Ability to digest animal tissues does not necessarily imply ability to digest casein, coagulated beef serum or gelatin.
10. The disappearance of the meat from cooked meat cultures of hemolytic streptococci is quantitatively roughly paralleled by increase of formol-titrable substances in the fluid portion of the medium.
11. The enzyme resembles trypsin in its action. Streptococci from a variety of sources, bovine, human and otherwise have shown varying degrees of proteolytic activity.
12. The name histase is proposed for this enzyme.